Keep frame shared memory mapped (#24644)

* keep frame shm open and skip overwritten frames

Every reader closed and reopened a frame's shared memory segment on each frame, so each process paid a page fault on every page of a fresh mapping (about 760 for a 1080p frame) per frame. Readers now keep segments mapped. Capture stamps each slot's frame time in a per-camera `{camera}_frame_times` segment, and `get()` returns None when the slot no longer holds the requested frame, reopening once by name so a mapping left over from a same-size camera recreate heals itself. Capture also reuses a slot when the frame queue is full, since no reader was told about it.

* verify the frame for embeddings object updates

Tracked object events only carried the object's own frame_time, which stays at its last detection when the object isn't detected in a frame, so embeddings couldn't check the slot it read and could crop face or plate data from a frame that had already been overwritten. Events now carry the time of the frame they name, and embeddings passes it to `get()`.

* log when a frame slot was overwritten before it was read

A lapped read and a missing segment ended up as the same debug line at every caller, so there was no way to tell a slow reader from a missing frame.

* bring the FrameManager interface in line with its implementation

The abstract get() still had a timeout_ms signature from an older implementation and frame_times() wasn't declared, though capture and detect are typed against the interface. get() also didn't say how long the array it returns stays valid.

* drop a camera's cached frame mappings when it is removed or recreated

A reader that kept its mappings open stayed on a removed camera's segments, which pinned their shared memory until restart, and after a same-size recreate the ledger reopen only refreshed the slot being read while the other cached slots still returned the old camera's pixels. Readers now drop every cached slot for a camera on its remove update, and get() does the same when a ledger mismatch turns out to be a replaced ledger rather than a lapped slot.

* match a camera's frame names exactly in close_camera

The prefix match on `{camera}_frame` also caught another camera whose name starts with it, so removing `cam` dropped the cached ring of a camera named `cam_frame`.

frigate/review/maintainer.py

@@ -504,6 +504,7 @@ class ReviewSegmentMaintainer(threading.Thread):
     def _handle_camera_removed(self, camera: str) -> None:
         """Close out a deleted camera's segment so a reused name cannot inherit it."""
         self.forcibly_end_segment(camera)
+        self.frame_manager.close_camera(camera)
         self.indefinite_events.pop(camera, None)
         self.recent_classification_state_changes.pop(camera, None)
 
@@ -544,7 +545,7 @@ class ReviewSegmentMaintainer(threading.Thread):
 
         try:
             yuv_frame = self.frame_manager.get(
-                frame_name, camera_config.frame_shape_yuv
+                frame_name, camera_config.frame_shape_yuv, frame_time
             )
         except FileNotFoundError:
             return
@@ -554,7 +555,6 @@ class ReviewSegmentMaintainer(threading.Thread):
             return
 
         pending.update_frame(camera_config, yuv_frame, objects)
-        self.frame_manager.close(frame_name)
 
     def update_existing_segment(
         self,
@@ -653,7 +653,7 @@ class ReviewSegmentMaintainer(threading.Thread):
                 try:
                     if should_update_image:
                         yuv_frame = self.frame_manager.get(
-                            frame_name, camera_config.frame_shape_yuv
+                            frame_name, camera_config.frame_shape_yuv, frame_time
                         )
 
                         if yuv_frame is None:
@@ -669,7 +669,6 @@ class ReviewSegmentMaintainer(threading.Thread):
                         activity.get_all_objects(),
                         prev_data,
                     )
-                    self.frame_manager.close(frame_name)
                 except FileNotFoundError:
                     return
 
@@ -677,7 +676,7 @@ class ReviewSegmentMaintainer(threading.Thread):
             if not segment.has_frame:
                 try:
                     yuv_frame = self.frame_manager.get(
-                        frame_name, camera_config.frame_shape_yuv
+                        frame_name, camera_config.frame_shape_yuv, frame_time
                     )
 
                     if yuv_frame is None:
@@ -685,7 +684,6 @@ class ReviewSegmentMaintainer(threading.Thread):
                         return
 
                     segment.save_full_frame(camera_config, yuv_frame)
-                    self.frame_manager.close(frame_name)
                     self._publish_segment_update(
                         segment, camera_config, None, [], prev_data
                     )
@@ -770,7 +768,7 @@ class ReviewSegmentMaintainer(threading.Thread):
 
                 try:
                     yuv_frame = self.frame_manager.get(
-                        frame_name, camera_config.frame_shape_yuv
+                        frame_name, camera_config.frame_shape_yuv, frame_time
                     )
 
                     if yuv_frame is None:
@@ -780,7 +778,6 @@ class ReviewSegmentMaintainer(threading.Thread):
                     new_segment.update_frame(
                         camera_config, yuv_frame, activity.get_all_objects()
                     )
-                    self.frame_manager.close(frame_name)
                     self._publish_segment_start(new_segment)
                 except FileNotFoundError:
                     return